RESUMEN
Specimens were obtained from the 3 Malagasy fruit bats, Pteropus rufus, Eidolon dupreanum, and Rousettus madagascariensis. Antibodies against Nipah, Hendra, and Tioman viruses were detected by immunoassay in 23 and by serum neutralization tests in 3 of 427 serum samples, which suggests that related viruses have circulated in Madagascar.
Asunto(s)
Quirópteros/virología , Paramyxoviridae/inmunología , Animales , Anticuerpos Antivirales/sangre , MadagascarRESUMEN
Lassa fever is a hemorrhagic fever caused by Lassa virus (LV), which primarily targets human dendritic cells (DC) and macrophages (MP). Massive numbers of viral particles are released with no effect on the viability, activation or maturation of these cells. LV does not inhibit the activation of cells induced by sCD40L or LPS. We report here the consequences of exogenous activation of LV-infected human DC and MP for viral replication. The activation of cells with lipopolysaccharide or exogenous poly(I-C) and the transfection of cells with poly(I-C) strongly inhibited LV replication, at least partly by inducing type I interferon (IFN) synthesis. In contrast, cell stimulation with sCD40L did not induce type I IFN responses or inhibit LV release. Recombinant type I IFNs strongly inhibited LV replication in both cell types, whereas IFNgamma and IFNlambda did not. The modest type I IFN production observed in LV-infected MP, but not in DC, was involved in controlling LV replication in MP. These results provide an explanation for the slower replication of LV in MP than in DC, and suggest that type I IFNs are crucial in the control of LV.
Asunto(s)
Células Dendríticas/virología , Interferones/farmacología , Virus Lassa/fisiología , Macrófagos/virología , Replicación Viral/efectos de los fármacos , Animales , Células Presentadoras de Antígenos/inmunología , Células Presentadoras de Antígenos/metabolismo , Células Cultivadas , Chlorocebus aethiops , Células Dendríticas/inmunología , Humanos , Interferón Tipo I/metabolismo , Interferón Tipo I/farmacología , Interferones/metabolismo , Virus Lassa/efectos de los fármacos , Activación de Macrófagos , Macrófagos/inmunología , Células VeroRESUMEN
We conducted a survey in Cambodia in 2000 on henipavirus infection among several bat species, including flying foxes, and persons exposed to these animals. Among 1,072 bat serum samples tested by enzyme-linked immunosorbent assay, antibodies reactive to Nipah virus (NiV) antigen were detected only in Pteropus lylei species; Cynopterus sphinx, Hipposideros larvatus, Scotophilus kuhlii, Chaerephon plicata, Taphozous melanopogon, and T. theobaldi species were negative. Seroneutralization applied on a subset of 156 serum samples confirmed these results. None of the 8 human serum samples was NiV seropositive with the seroneutralization test. One virus isolate exhibiting cytopathic effect with syncytia was obtained from 769 urine samples collected at roosts of P. lylei specimens. Partial molecular characterization of this isolate demonstrated that it was closely related to NiV. These results strengthen the hypothesis that flying foxes could be the natural host of NiV. Surveillance of human cases should be implemented.
Asunto(s)
Quirópteros/virología , Infecciones por Henipavirus/veterinaria , Virus Nipah/aislamiento & purificación , Animales , Cambodia/epidemiología , Infecciones por Henipavirus/epidemiología , Infecciones por Henipavirus/virología , Humanos , Virus Nipah/genética , FilogeniaRESUMEN
Lassa virus (LV) and Mopeia virus (MV) are closely related members of the Arenavirus genus, sharing 75% amino acid sequence identity. However, LV causes hemorrhagic fever in humans and nonhuman primates, whereas MV cannot induce disease. We have previously shown that antigen-presenting cells (APC)-macrophages (MP) and dendritic cells (DC)-sustain high replication rates of LV but are not activated, suggesting that they play a role in the immunosuppression observed in severe cases of Lassa fever. Here, we infected human APC with MV and analyzed the cellular responses induced. MV infection was productive in MP and even more so in DC. Apoptosis was not induced in either cell type. Moreover, unlike DC, MP were early and strongly activated in response to MV, as shown by the increased surface expression of CD86, CD80, CD54, CD40, and HLA-abc and by the production of mRNA encoding alpha interferon (IFN-alpha), IFN-beta, tumor necrosis factor alpha and interleukin-6. In addition, MV-infected MP produced less of the virus than DC, which was related to the fact that these cells secreted IFN-alpha. Thus, the strong activation of MP is probably a major event in the control of MV infection and may be involved in the induction of an adaptive immune response in infected hosts. These results may explain the difference in pathogenicity between LV and MV.
Asunto(s)
Arenavirus del Viejo Mundo/inmunología , Arenavirus del Viejo Mundo/fisiología , Células Dendríticas/inmunología , Interferón-alfa/metabolismo , Interferón beta/metabolismo , Macrófagos/inmunología , Células Presentadoras de Antígenos/inmunología , Células Presentadoras de Antígenos/virología , Antígenos CD/biosíntesis , Apoptosis , Antígeno B7-1/biosíntesis , Antígeno B7-2 , Antígenos CD40/biosíntesis , Células Cultivadas , Células Dendríticas/virología , Antígenos HLA-A/biosíntesis , Antígenos HLA-B/biosíntesis , Antígenos HLA-C/biosíntesis , Humanos , Molécula 1 de Adhesión Intercelular/análisis , Molécula 1 de Adhesión Intercelular/biosíntesis , Interferón-alfa/genética , Interferón beta/genética , Interleucina-6/genética , Interleucina-6/metabolismo , Activación de Macrófagos , Macrófagos/virología , Glicoproteínas de Membrana/biosíntesis , ARN Mensajero/análisis , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Necrosis Tumoral alfa/genética , Factor de Necrosis Tumoral alfa/metabolismo , Ensayo de Placa Viral , Replicación ViralRESUMEN
Nipah and Hendra viruses belong to the novel Henipavirus genus of the Paramyxoviridae family. Its zoonotic circulation in bats and recent emergence in Malaysia with fatal consequences for humans that were in close contact with infected pigs, has made the reinforcement of epidemiological and clinical surveillance systems a priority. In this study, TaqMan RT-PCR of the Nipah nucleoprotein has been developed so that Nipah virus RNA in field specimens or laboratory material can be characterized rapidly and specifically and quantitated. The linearity of the standard curve allowed quantification of 10(3) to 10(9) RNA transcripts. The sensitivity of the test was close to 1 pfu. The kinetics of Nipah virus production in Vero cells was monitored by the determination of infectious virus particles in the supernatant fluid and by quantitation of the viral RNA. Approximately, 1000 RNA molecules were detected per virion, suggesting the presence of many non-infectious particles, similar to other RNA viruses. TaqMan real-time RT-PCR failed to detect Hendra virus DNA. Importantly, the method was able to detect virus despite a similar ratio in viremic sera from hamsters infected with Nipah virus. This standardized technique is sensitive and reliable and allows rapid detection and quantitation of Nipah RNA in both field and experimental materials used for the surveillance and specific diagnosis of Nipah virus.
Asunto(s)
Virus Nipah/aislamiento & purificación , ARN Viral/análisis , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Animales , Línea Celular , Cricetinae , Humanos , Mesocricetus , Virus Nipah/genética , ARN Viral/aislamiento & purificación , Sensibilidad y Especificidad , Especificidad de la Especie , Polimerasa TaqRESUMEN
Lassa fever is a hemorrhagic fever caused by Lassa virus (LV), an old-world Arenavirus. Little is known about the immune responses that occur during the disease, but protection seems to be linked to the induction of cellular responses specific for viral glycoproteins. Conversely, severe Lassa fever may be associated with immunosuppression. We studied the infection of human dendritic cells (DC) and macrophages (MP) by LV. Both these cell types are susceptible to LV infection. Viral nucleoprotein was detected in DC and MP, and high and moderate viral titers were obtained with culture supernatants of DC and MP, respectively. LV did not induce apoptosis in DC and MP. These cells were not activated by LV infection. No change was observed in the expression of surface molecules involved in activation, costimulation, adhesion, and Ag presentation following LV infection, or in the functional properties of DC. Inflammatory cytokine production was not detected at the mRNA or protein level after LV infection of DC and MP. Thus, MP, and particularly DC, are crucial targets for LV and are probably involved in the early replication of LV from the initial site of infection. The lack of activation and maturation of cells following infection may be associated with the immunosuppression observed in severe LV infection.